Finned tube and method for forming the same



June 13, 1939.

,E. F. LEDBETTER FINNED TUBE AND METHOD FOR FORMING THE SAME Filed Got. 7, 1935 Flfiml FIG .4.

ATTORNEYS M TR Nu ET m B [D E L EM R w E M L E M? w. Y B

Patented June 13, 1939 UNITED STATES PATENT OFFICE FINNED TUBE AND METHOD FOR FORMING THE SAME The invention relates to finned tubes such as used in radiators of various types, for the absorption or dissipation of heat. It is the object of the invention to obtain a simple construction and method of manufacture of the same, having among other advantages, first, that it permits of making the tubes and the fins of dissimilar metals; second, that it forms a very effective means for heat transfer; third, that it securely connects the fins to the tubes, and fourth, that it lends itself to manufacture and assembly by automatic machines. With these objects in view the invention consists in the construction and method as hereinafter set forth. 5 In the drawing:

Figure 1 is a side elevation of one of the fins;

Figure 2 is an edge elevation thereof;

Figure 3 is a perspective view illustrating the manner of securing the fins to the tubes;

Figure 4 is an enlarged section in the axial plane of the tube illustrating the attachment between the fins and the tubes;

Figure 5 is a side elevation of a portion of the completed structure;

2 Figure 6 is a view similar to Figure 4 showing a modified construction.

With radiators of the tube and fin type, efficiency in heat transfer is dependent upon the rate of conduction through the joint between the tube and fins and this in turn is dependent upon the extent of actual contact surface between these members. The-re is also the problem of mechanically mounting and securing the fins upon the tubes so as to permit of quick assembly and to produce good contact in the joints. Still further, it is desirable to manufacture the fins with a minimum waste of metal. I have therefore devised a construction in which separate split fins apertured to surround the tube and provided with laterally extending contact flanges are secured by a continuous strip wound spirally about these flanges and passing through the splits in the successive fins. By this means the flanges are pressed into firm contact with the outer surface of the tube so as to produce a high rate of heat conduction therebetween. The construction is also one which can be manufactured at low cost and which as above stated lends itself to assembly by automatic machines. As illustrated, A are the fins which are cut from sheet metal with a central aperture B corresponding to the size of the tube and with. a lateral flange C struck out tosurround this aperture. In the forming of these fins they are split along a radial line D which also extends through the flange C. The fins thus constructed are mounted upon a tube such as E, and the portion A upon one side of the split in each fin is laterally deflected from the portion A on the opposite side of the split, so as to come substantially 5 into alignment with the corresponding portion A of the adjacent fin. A strip G is then wound spirally around the tube E and flanges C passing through the spaces between the portions A, A and. so on continuously throughout the length 10 of the tube. This strip G constitutes a spacer between fins and also a binding means for clamping the flanges C against the outer face of the tube so as to obtain good contact. As specifically shown, the strip G is in the form of a channel 16 member, the web portion G contacting with the flanges C and the side flanges G of the strip lying adjacent to the fins. Thus in addition to the conduction between the tube and the flanges C heat is also transferred through the web G and 2,

flanges G into the fins.

The method of assembly just described is one which could be performed manually but it is obvious that-it is also one which might be performed by an automatic machine. However, the construction of such machine forms no part of the present invention.

In assembling the spacer strip G it may sometimes be found desirable to have the strip at an elevated temperature during the winding opera- 39 tion, thus causing a more intimate contact due to the shrinkage of the metal after the strip has cooled to the same temperature as the remainder of the structure. It is also within the purview of the invention to form a construction 35 in which the lateral flange C is wholly or partially omitted. In such case the spacing strip G will contact directly with the outer surface of the tube E as illustrated in Figure 6. In this figure the unflanged fins A? are mounted on the tube 40 E. The flanged spacing strip G is spirally wound on the tube E contacting directly therewith. The

flanges G contact with the sides of the fins A thereby serving to conduct'the heat from the tube to the flns. I 45 It is also to be understood that the spacer strip G may be of any desirable cross section whereby it may be spirally wound around the tube intermediate the fins.

What I claim as my invention is: 50 1. Themethod of manufacturing finned tubes comprising the forming of a series of fins from sheet metal, each fin having a central aperture with a laterally extending flange surrounding the same and being split radially through both 56 fin and flange, mounting a series of fins upon the tube with the portions upon opposite sides of the split in each fin laterally'deflected, and

spirally winding a binding strip around said tube and the laterally extending flanges of the fins, said strip being tensioned to press said flanges.

in firm contact with the outer surface of the tube and passing successively through the radial splits of one fin into engagement with an adjacent fin.

. the web portion of said stripcontacting with said annular'flanges and the flanges of the strip contacting with adjacent fins to form additional heat conducting means between said tube and fins.

3. The method of manufacturing finned articles comprising the forming of a series of radially split sheets centrally apertured and eachprovi'ded with a laterally extending portion surrounding said aperture, mounting said sheets upon a core member with the portions upon opposite sides of the split in each sheet laterally deflected, spirally winding a binding strip around said core member and laterally extending por- 1 -tions of the sheets, said strip passing successively through the spaces between deflected portions of .said sheets and heating said binding strip prior a series of radially split fins sleeved upon said core member, each fin having a laterally extending portion surrounding the core and the-portions on opposite sides of the split being laterally deflected to form a space therebetween, and aspirallywound binding strip surrounding said core member and laterally extending portions of the fins passing successively through the splitsin each 5. A finned article comprising a core member, a series ofradially split sheets mounted on said core member, each sheet having a laterally extending annular split flange surrounding the core member, the portions on opposite sidesof the split beinglaterally deflected to form a space therebetween, said sheets extending radially outward from said core member for a distance not substantially less than the diameter of said core member and a spirally wound binding strip surrounding said core member and laterally extending portions of the" sheets and passing successively through the splits in each sheet.

ELMER E LEDBETI'ER. 

